Rassf2 overexpression mediated by AAV promotes the supporting cell-to-hair cell transformation in the cochlea

Sensory hair cells are responsible for detecting and transmitting sound in the inner ear,and damage to HCs leads to hearing loss.HCs do not regenerate spontaneously in adult mammals,which makes the hearing loss permanent.However,hair cells and supporting cells have the same precursors in the inner ear,and in newborn mice,the adjacent SCs can be activated by gene manipulation to differentiate into newly regenerated hair cells.Here,we demonstrate the role of the Ras association domain family member 2(Rassf2)in supporting cell to hair cell trans-differentiation in the inner ear.Using the AAV vector(AAV-ie)to upregulate Rassf2 expression promoted supporting cell division and hair cell production in cultured cochlear organoids.Also,AAV-Rassf2 enhanced the regenerative ability of Lgr5+SCs in the postnatal cochlea without impairing hearing,and this might due to the modulation of the Wnt,Hedgehog and Notch signaling pathways.Furthermore,AAV-Rassf2 enhances cochlear supporting cell division and hair cell production in the neomycin injury model.In summary,our results suggest that Rassf2 is a key component in HC regenerative repair,and gene modulation mediated by adeno-associated virus may be a promising gene therapy for hearing repair.

TGFβ signaling hyperactivation-induced tumorigenicity during the derivation of neural progenitors from mouse ESCs

Clinical therapies of pluripotent stem cells （PSCs）-based transplantation have been hindered by frequent development of terato- mas or tumors in animal models and clinical patients. Therefore, clarifying the mechanism of carcinogenesis in stem cell therapy is of great importance for reducing the risk of tumorigenicity. Here we differentiate Oct4-GFP mouse embryonic stem cells （mESCs） into neural progenitor cells （NPCs） and find that a minority of Oct4＋ cells are continuously sustained at Oct4＋ state. These cells can be enriched and proliferated in a standard ESC medium. Interestingly, the differentiation potential of these enriched cells is tightly restricted with much higher tumorigenic activity, which are thus defined as differentiation-resistant ESCs （DR-ESCs）. Transcriptomic and epigenomic analyses show that DR-ESCs are characterized by primordial germ cell-like gene sig- natures （Dazl, Rec8, Stro8, BUmp1, etc.） and specific epigenetic patterns distinct from mESCs. Moreover, the DR-ESCs possess germ cell potential to generate Sycp3＋ haploid cells and are able to reside in sperm-free spermaduct induced by busulfan. Finally, we find that TGFβ signaling is overactivated in DR-ESCs, and inhibition of TGFβ signaling eliminates the tumorigenicity of mESC-derived NPCs by inducing the full differentiation of DR-ESCs. These data demonstrate that these TGFβ-hyperactivated germ ceU-like DR-ESCs are the main contributor for the tumorigenicity of ESCs-derived target cell therapy and that inhibition of TGFβ signaling in ESC-derived NPC transplantation could drastically reduce the risk of tumor development. Keywords： embryonic stem cells, differentiation-resistant ESCs, tumorigenicity, germ cell, TGFβ signaling

AAV-ie-K558R mediated cochlear gene therapy and hair cell regeneration

The cochlea consists of multiple types of cells,including hair cells,supporting cells and spiral ganglion neurons,and is responsible for converting mechanical forces into electric signals that enable hearing.Genetic and environmental factors can result in dysfunctions of cochlear and auditory systems.In recent years,gene therapy has emerged as a promising treatment in animal deafness models.One major challenge of the gene therapy for deafness is to effectively deliver genes to specific cells of cochleae.

A protective AAV vaccine for SARS-CoV-2

Dear Editor,Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)has caused the COVID-19 pandemic,with more than 528 million infections and 6.2 million deaths.To fight against this rapidly spreading pandemic,prophylactic vaccines have been developed using different techniques,such as inactivated virus,messenger RNAs,recombinant proteins,and viral-vectored vaccines.However,rapidly spreading variants of SARS-CoV-2,such as alpha,beta,delta,and omicron variants,have been emerging.